“No trespassing” alerts passing individuals that they are near a private land boundary and also excuses the landowner of some liability if people visit uninvited.
Sometimes, the warning and limitation of liability are based on statutory law. For example, the state of Washington in the United States has a law that prevents people injured at equestrian facilities from pursuing legal damages.
Any business that boards, trains or allows the riding of horses has to have a specific sign to enjoy this protection from liability. This sign acts as a disclaimer much like a “No trespassing” sign in that it informs and specifies limits on facility responsibilities: